Nice idea! Definitely gives me flappy bird vibes. I also like the idea for the ability to become slimmer with the spacebar to fit through tight spaces but there also wasn't a limit on that so I just held it forever haha. Would have appreciated an infinite shoot option as my finger started getting tired from constantly clicking.
Also good job with the procedural generation on the cave systems! Its always cool to have games that are different when you open them up again.